The present invention relates to a body probe for MRI and an MRI apparatus using the probe; and, more particularly, the invention relates to a body probe for MRI, which is easy to use and provides clear images without image degradation, and an MRI apparatus using the probe.
In general, a body probe for MRI comprises two reception coils that are to be positioned above and under a subject to be examined (examinee). A typical body probe for MRI has upper and lower coils formed integrally into a cylindrical shape or a cylindrical shape which can be partly opened sideways, or a belt-like shape.
FIGS. 11A and 11B are diagrams which show one structural example of a body probe for MRI. Referring to the figures, xe2x80x9c111xe2x80x9d denotes a body probe, xe2x80x9c112xe2x80x9d denotes a body portion and xe2x80x9c113xe2x80x9d denotes a window. The body probe 111 exemplified in FIGS. 11A and 11B has a cylindrical shape.
As shown in FIG. 11A, the body probe 111 comprises a cylindrical body portion 112 which has a length and internal vertical and horizontal sizes that are long and large enough to cover the chest of a subject to be examined. The windows 113 are formed in the top and bottom portions on both sides of the body portion 112 in order to lighten the overall weight of the body probe and permit the position of the subject with respect to the body probe to be checked from the outside. Though not illustrated, reception coils are embedded in the body portion 112 and are connected to an MRI apparatus, so that signals from the coils can be processed to form an image to be displayed.
FIG. 11B shows how the cylindrical body probe 111 is used. A subject to be examined, whose chest is enclosed by the body probe 111, is placed inside an MRI apparatus for examination. Generally speaking, the size of a person""s chest varies from one person to another. It is therefore difficult to prepare a probe which precisely matches the size of the chest of each subject, and such an attempt inevitably results in an increase in the cost of the entire MRI system. For this reason, normally, three or so different sizes of body probes 111 are prepared and used for all subjects of different builds.
Although the body probe exemplified in FIGS. 11A and 11B is designed to be completely cylindrical, there is a body probe designed in such a way that it can be opened sideways at the center portion.
FIG. 12 is a diagram showing another structural example of a body probe for MRI. In FIG. 12, xe2x80x9c121xe2x80x9d denotes an opening, xe2x80x9c122xe2x80x9d denotes an upper coil, xe2x80x9c123xe2x80x9d denotes a lower coil, xe2x80x9c124xe2x80x9d denotes a belt, xe2x80x9c125xe2x80x9d denotes cords, and xe2x80x9c126xe2x80x9d denotes a connector box.
The body probe for MRI exemplified in FIG. 12 has reception coils, which comprise the upper coil 122 and the lower coil 123. In using the body probe, the lower coil 123 and the upper coil 122 are secured by the belt 124. The lower coil is placed under the back of a subject to be examined and the upper coil is placed over the abdominal portion, the chest or the like of the subject. The belt 124 is attached to a belt groove provided in the frame of a bed in such a way as to be movable along the bed to secure the subject at a desired portion. The belt 124 is movable in accordance with the mounting position of the upper coil 122. The body probe for MRI which has the above-described structure can securely fix the upper coil 122 and the subject together.
The cords 125 that extend from the upper and lower coils run along one edge portion of the bed and are connected to the connector box 126 located inside the opening 121 of the MRI apparatus. At the time of picking up an image with the MRI apparatus, the subject is moved into the opening 121 to a predetermined position together with the top table of the bed and the connector box 126.
The cylindrical body probes for MRI as described above do not have fixed distances between the subject and the coils in the body probe due to a difference in the build of the subject, and difficulty is experienced in securing the subject inside the body probe. This makes the characteristics of the coils unstable, so that picked-up image of the subject is degraded by movement of the body of the subject. The cylindrical body probe also has a shortcoming in that it is not easily attached to a subject.
Another body probe for MRI, whose reception coils comprise an upper coil and a lower coil, has no coil portions provided at portions corresponding to the sides of the subject. In addition, it is difficult to place the center of the upper coil over the center of the body axis of the subject, so that the center of the upper coil may be misaligned with respect to the center of the body axis of the subject. This makes it difficult to acquire clear images.
With regard to use of a belt-like body probe, one among several sizes of body probes which matches the build of a subject to be examined is selected and is fitted on the subject. This type of body probe cannot restrain movement of the body of the subject, so that the body probe moves as the body of the subject moves. This also leads to image degradation.
The reception coils of the above-described body probes are cylindrical or belt-like and their sizes are not prepared subject by subject. Rather, one among several sizes of available body probes previously prepared, which is closest to the build of a subject to be examined, is selected. As the shapes of the reception coils become closer to the shape of the subject, the sensitivity becomes higher. To achieve a high sensitivity, therefore, it is necessary to fit the reception coils closely to the subject. On the contrary, the reception coils of the body probes of the type described above are difficult to fit closely to each subject to be examined.
Accordingly, it is an object of the present invention to provide an easy-to-use body probe for MRI, which is able to overcome the aforementioned problems, is easily attached to various subjects to be examined who have builds of different sizes and does not suffer image degradation, and an MRI apparatus which uses this probe.
The foregoing object is achieved by designing a body probe for MRI having reception coils for picking up an image for use in an MRI apparatus in such a way that the reception coils are provided in a center coil portion and two side coil portions.
The foregoing object is achieved by providing slide mechanisms for the side coil portions, which are formed by smooth surfaces, that are formed on both right and left sides of the center coil portion, at joint portions between the center coil portion and the side coil portions.
The foregoing object is achieved by designing a bottom surface of the center coil portion to have a curved shape, or providing an indicator indicating the center of the center coil at the center of a top surface of the center coil portion. The indicator indicating the center of the center coil may be a groove, a projection or a line drawn in a color different from the color around the line.
The foregoing object is also achieved by designing a body probe for MRI having reception coils for picking up an image for use in an MRI apparatus in such a way that the reception coils are provided in a center coil portion, side coil portions and a base coil portion. The center coil portion, the side coil portions and the base coil portion may be constructed independently of one another.
The foregoing object is achieved by constructing the side coil portions by embedding a flexible coil in a soft member, or by providing the side coil portions with cutaway holes at portions where there are no coil portions.
Other objects and structures of the invention and the resulting advantages thereof will become apparent from the following detailed description of an embodiment of the invention.